Fabrication of Homogeneous Nanometer‐Thin Artificial CEI on LNMO by Suspension Coating of Niobate Nanosheets

ABSTRACT Lithium‐ion batteries (LIBs) require stable high‐voltage cathode materials to meet escalating energy storage demands. LiNi 0.5 Mn 1.5 O 4 (LNMO) offers high energy density while employing earth‐abundant manganese but suffers from degradation due to manganese dissolution and electrolyte decomposition at elevated voltages. This work presents a facile water‐based process to coat LNMO particles with nanometer‐thin niobate nanosheets via electrostatically driven self‐assembly. As nanosheets of large aspect ratio (≈2000) are obtained by a spontaneous delamination yielding uniform thickness (1.8 nm), the coating consistently covers LNMO surfaces. Electrochemical testing in full‐cells showed improved cycle stability, enhanced rate capability, and reduced self‐discharge for coated LNMO compared to pristine material. Post‐cycling analyses revealed suppressed manganese migration to the anode, evidencing the coating's effectiveness as a Li‐ion‐conductive, chemically inert permselective membrane that mitigates detrimental side reactions. The modified LNMO/graphite full cells exhibit excellent cycling stability, retaining 91% of its initial capacity after 500 cycles at 1C, as compared to 42% for the pristine material. Additionally, the coated material shows an increased rate capability, with a capacity of 101 mAh g −1 at 5C as compared to 84 mAh g −1 of the uncoated. This scalable, cost‐effective, coating strategy extends cathode lifespan and offers a promising route for advancing high‐voltage LIB technology.